Ultrasonic wave delay line

ABSTRACT

An ultrasonic wave delay line comprising a delaying medium made up of a glass having a composition of, by weight, 57 to 78 percent SiO2, 0.5 to 9 percent Al2O3, 16 to 19 percent PbO, up to 11 percent Na2O, and up to 20 percent K2O, the combined amounts of Na20 + K2O being 9 to 20 percent and having temperature coefficient of time delay of not more than 5 X 10 6/*C in a wide temperature range, and an acoustic attenuation factor of less than 10 X 10 3 dB per cycle above 1 MHz.

United States Patent Inamura et a1.

[451 Oct. 30, 1973 ULTRASONIC WAVE DELAY LINE Inventors: Takahiro Inamura; Masao Ohno;

Muuehisa Tsunekawa; Yasuyuki Nakata, all of Tokyo, Japan Assignees: Nippon Telegraph & Telephone Public Corporation; Nippon Kogaku K.K., both of Tokyo, Japan Filed: Sept. 2, 1971 Appl. No.: 177,420

Related US. Application Data Continuation-impart of Ser. No. 811,964, April 1, 1969, abandoned.

Foreign Application Priority Data Apr. 5, 1968 Japan 43/22126 US. Cl. 333/30 R, 106/53 Int. Cl. 1103b 7/30, C03c 3/10, C03c 3/04 Field of Search 106/53; 333/30 References Cited UNITED STATES PATENTS 1/1945 Kalsing et a1. 106/53 10/1964 Hoover et a]. 106/53 3/1965 Hoover 106/53 FOREIGN PATENTS OR APPLICATIONS 1,807,831 8/1969 Germany 106/53 2,025,441 1/1971 Germany 106/53 Primary Examiner-A. B. Curtis Assistant Examiner-Mark Bell AttorneyAnton J. Wille [57] ABSTRACT 6 Claims, 2 Drawing Figures PATENIEDUBT 3 m 3.769513.

PIC-3.1

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PIC-3.2

(XIO' ULTRASONIC WAVE DELAY LINE The present application is a continuation-in-part of U.S. application Ser. No. 811,964 filed Apr. 1, 1969 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave delay line employing as the delaying medium a glass having a novel composition and excellent characteristics.

2. Description Of The Prior Art Generally, an ultrasonic wave delay line comprises a medium for transmitting ultrasonic waves therethrough, a transducer disposed upon a suitable portion of the surface of the medium for transducing electrical signals into mechanical ones and another transducer adapted to convert the mechanical signals to electrical ones. The simplest construction of the delay line of the type described comprises an input transducer and an output transducer attached to the respective ends of a medium. By the input transducer electrical signals are converted into mechanical signals (shear mode ultrasonic waves) which in turn transmit through the medium and reach the output transducer where the mechanical signals are again converted into the electrical signals. In this case, the signals are delayed by the time required for the mechanical signals to pass through the medium. That is, the delay time is defined as the time difference between the input and the output signals.

The characteristics of the delay line are dependent upon the delay time, the temperature coefficient of the delay time, and the amount of attenuation of the signals, etc. Various delay mediums having different shapes and being made of various materials have been proposed.

Generally the delay mediums are made of quartz, glass, ceramics, metals and the like; and mediums of the multireflection type have been also proposed to provide a compact delay line capable of increasing the delay time. I

The ultrasonic wave delay lines find many applica tions in the various fields such as television, radar, band width compression, electronic computers and so on. In this case, the delay lines are required to have asmaller temperature coefficient-of the delay time and less attenuation of the signals in the delaying medium. The conventional delay mediums made of molten quartz has a temperature coefficient of time delay of the order of about 8 X l= C, which is not sufficient for the use in the PAL system color television which requires a temperature coefficient of less than 3 X C. The problem has not been so far satisfactorily solved because even the improved glass'material exhibits a temperature coefficient of (l to 5) X 10' C. In the case of a multi-reflection type delay mediums, a precise machining operation is required so that glass is advantageous because of its machinability.

As to attenuation, quartz has the least attenuation factor among the glasses with a value of 2 X l 0 dB per cycle in measurements above 1 MHz. In case of ordinary glass, the attenuation factor is of the order of 10 X 10' to 50 X 10' dB, which is far from the value satisfactorily applied in practice.

SUMMARY OF THE INVENTION In view of the above the primary object of the present invention is to provide an ultrasonic wave delay line having a smaller temperature coefficient of time delay and a smaller signal attenuation factor than heretofore attainable.

According to the present invention, the temperature T at which the delay time becomes minimum can be varied even in the temperature range slightly deviated from the normal temperature by suitably selecting the composition of the ultrasonic wave transmission medium. For example, when the service temperature range is from to C, the temperature coefficient of delay time of the delay line of the present invention can be made less than 1.5 X 10/ C.

In brief, the present invention provides an ultrasonic wave delay line incorporating a delaying medium made of a glass having the composition of, by weight, '57 to 78 percent SiO 0.5 to 9 percent Al O 16 to 19 percent PbO; up to 11 percent Na O and upto 20 percent K 0; the combined amounts of Na O and K 0 being from 9 to 20 percent, and having a temperature coefficient of time delay of not more than 5 X l0' C over a wide temperature range centered around room temperature, and an acoustic attenuation factor of less than 10 X 10 dB per cycle about 1 MHz. In the foregoing embodiment, a desired temperature coefficient of time delay is l X 10/" C to 5 X 10 C. In the foregoing embodiment a suitable amount of K 0 is l to 7 weight percent. In the foregoing embodiment a suitable amount of Na O is 6 to l 1 weight percent. In the foregoing embodiment a desired amount of SiO is 60 to 67 weight percent. Also, in the foregoing embodiment the desired amount of PhD is 17 weight percent.

The temperature coefficient of time delay'can be controlled by the composition of the glass when it is cooled sufficiently gradually, but generally varies depending upon the temperature range selected. The relation betweenthe time delay 1' and the deviation A1- due to temperature difference can be expressed by where a a constant;

T temperature at which the delay time is minimum; and T temperature measured.

It is seen from the equation that in order to reduce the temperature coefficient, it is required that T must be at the middle of the selected service temperature.

In the glass of the present invention having the composition described above, the ingredients SiO A1 0 and PhD have the characteristic of shifting T, to the positive side; A1 0 has a great influence in this respect while PbO has a small influence. On the other hand, M1 0 and K 0 have the tendency of shifting T to the negative side. Of the two, Na O is stronger than K 0. Therefore, by suitably selecting the ratios of these ingredients, the temperature T may be centered in the service temperature range.

However, the delay line is used generally at room temperature so that when (Na O K 0) is in excess of 20 percent by weight, the amount of the remaining ingredients is not sufficient enough to shift the temperature T to the positive side, thereby lowering the temperature T to a temperature far lower than room temperature. On the other hand, when (Na O K 0) is less than 9 percent by weight, the temperature T, will be increased far higher than room temperature. Thus, when (Na O K is between 9 percent and 20 percent by weight, a suitable combination of other ingrediems of 57 to 78 percent by weight of SiO l6 to l9 percent by weight of H; and 0.5 to 9 percent by weight of Al O can set the temperature T close to room temperature.

According to the present invention, in addition to the above described ingredients, less than 10 percent by weight of glass forming oxides or fluorides such as $13 0 or AS 0 may be added as a clarifier.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in more detail with reference to the accompanying drawings in which:

FIG. 1 shows a typical bar-shaped delay line; and

FIG. 2 is a graph illustrating the relation between the rate of change of delay time and temperature of examples of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In Table 1 are shown the compositions (No. l to N0. 9) of the glasses embodying the present invention with the ingredients being within the above described ranges and compositions (No. 10 to No. 12) of ordinary glass (flint glass); and the corresponding temperature coefficients of time delay over the temperature range of 0 to 50 C.

TABLE 2 Temperature coellicients in X10-/ C. Glass a( 10-"/ 'I Nos. 0 to 50 C. 15 to 05 C. 30 to 80 0. (1.) C.)

5 1.0 1.8 2.5 2.3 4.5 7 l. 3 2.] 4. (i 8. 8 28. 0 4 1.0 o. t; 1. 3 3. 6 37. 5 ti 2. 7 l. 6 0. 7 4. 0 5!). 5

There is a relation of A-r/T A (T T as described before so that it is preferable to use the glass having a specific temperature T in such a temperature range from T, C to T, C which satifies approximately the relation of 2T T T as is clearly seen from FIG. 2 and Table 2. For example, in case of the glass, Nos. 5 and 7 in Table 2, the service temperature range is from 0 to 50 C; in case of No. 4, from l5 to 65 C; and in case of No. 6, from 30 to 80 C.

The present invention has been so far described with particular reference to some embodiments thereof, but it will be understood that variations and modifications can be effected without departing from the true spirit of the present invention.

We claim:

1. An ultrasonic delay line comprising a glass delay medium having a temperature coefficient of time delay of not more than 5 X l0 C and an attenuation factor of less than 10 X 10 dB per cycle above 1 MHz, and input and output transducers sealed to the facets on the delay medium, said delay medium consisting essentially of, by weight, 57 78 percent SiO 0.5 to 9 percent A1 0 16 to 19 percent PbO, up to ll percent Na O, and up to 20 percent K 0, the combined amounts of TABLE 1.COMPOSITIONS IN PERCENT BY WEIGHT Glass No 1 2 3 4 5 6 7 8 'J 10 11 12 Composition:

As will be clearly seen from Table 1, all glasses of the present invention have smaller temperature coefficients of delay time than that of the ordinary glasses, the attenuation factors have been measured to be less than 10 X 10 dB per cycle above 1 MHz. For example, glass No. 5 has an attenuation factor of 8 X 10' dB per cycle when measured at a frequency of 5 MHz.

The relations between the temperature and the rate of change in delay time of the glass of Table l are shown in FIG. 2, and the temperature coefficients of delay times obtained from these curves are shown in Table 2. V

Na O and K 0 being 9 to 20 percent.

2. An ultrasonic delay line according to claim I,

wherein the amount of PbO is l? weight percent. 

2. An ultrasonic delay line according to claim 1, wherein the temperature coefficient of time delay of 1 X 10 6/* C to 5 X 10 6/* C.
 3. An ultrasonic delay line according to claim 1, wherein the amount of K2O is 1 to 7 weight percent.
 4. An ultrasonic delay line according to claim 1, wherein the amount of Na2O is 6 to 11 weight percent.
 5. An ultrasonic delay line according to claim 1, wherein the amount of SiO2 is 60 to 67 weight percent.
 6. An ultrasonic delay line according to claim 1, wherein the amount of PbO is 17 weight percent. 